This invention relates to optical heads used to write data to and read data from an optical disk, and in particular to a system and method for aligning the components of a miniature optical head for use in a personal electronic device such as a audio player or digital camera.
The increasing miniaturization of computers and personal electronic devices (PEDs) has led to a need for extremely small components. The above-referenced application Ser. No. 09/457,104 describes a low profile optical head, used in optical disk storage devices, that can have a height (measured perpendicular to the optical disk) of, for example, 3.25 mm. A feature of the head is that its components are rigidly attached to each other with a permanent adhesive and cannot be adjusted after the head has been assembled. This distinguishes this head from the larger optical heads used in, for example, conventional compact disk (CD) players, where the light source or lens can be adjusted after assembly to ensure that the read-write beam is properly aligned with respect to the objective lens and photodetector.
A need exists, therefore, for an apparatus that can be used to properly align the extremely small components (light source, mirrors, lenses, etc.) in a low profile optical head.
This need is answered by the system and method of this invention. According to this invention, a system for aligning the components of an optical head comprises a rotational stage; a first mechanical path extending from a first side of the rotational stage, the first mechanical path comprising a first X-translation stage and a first Y-translation stage; a first holding mechanism attached to an end of the first mechanical path for holding a first component of the optical head; a second mechanical path extending from a second side of the rotational stage, the second mechanical path comprising a second X-translation stage and a second Y-translation stage; a second holding mechanism attached to an end of the second mechanical path for holding a second component of the optical head; and a Z-translation stage positioned so as to alter the spacing between the first and second holding mechanisms in a Z direction. The system also comprises a first microscope for viewing the first and second components of the optical head in a Z direction and a second microscope for viewing the first and second components of the optical head in a direction perpendicular to the Z direction.
In one embodiment, the first mechanical path comprises a stack comprising the first X-translation stage and the first Y-translation stage, the stack being mounted on the rotational stage. The first holding mechanism is mounted on the first Y-translation stage. The rotational stage is mounted on the second Y-translation stage, and the second Y-translation stage is mounted on a base member. The second X-translation stage is also mounted on the base member, and the Z-translation stage is mounted on the second X-translation stage. The second holding mechanism is mounted on the Z-translation stage. In addition, in this embodiment the system comprises a tracking actuator for holding a piece of optical media, an analog circuit for electrical connection to a component of an optical head held by one of the first and second holding mechanisms, and an oscilloscope electrically connected to the analog circuit. The tracking actuator is driven by a low-frequency oscillator and vibrates the piece of optical media in a direction parallel to the surface thereof and perpendicular to the data tracks on the surface thereof. The system can also comprise a focus actuator which is likewise driven by a low-frequency signal and vibrates the piece of media in a direction perpendicular to the surface thereof. By viewing the signals shown on the oscilloscope, the operator can determine whether the components of the optical head are correctly aligned before assembly.
This invention also includes a system for aligning the components of an optical head comprising a first holding device; a second holding device; a mechanical path extending between the first and second holding devices, the mechanical path comprising: a rotational stage; a first X-translation stage and a first Y-translation stage; a second X-translation stage and a second Y-translation stage; and a Z-translation stage positioned so as to alter the spacing between the first and second holding mechanisms in a Z direction.
This invention also includes a method of assembling the components of an optical head. The method comprises positioning first and second components of the optical head adjacent to each other; connecting the first component to a source of electrical power to energize a light source within the first component and thereby produce a light beam, the light beam following a forward path out of the first component and into, through and out of the second component; translating the first component in X and Y directions until the light beam emerging from the first component on a first section of the forward path coincides with a predetermined Z-axis; translating the second component in the X and Y directions until the light beam emerges from the second component on a second section of the forward path at a predetermined location on the second component; reflecting the light beam along a return path into, through and out of the second component; and rotating the first component about the Z-axis until the light beam in the return path strikes the first component at a predetermined location. The method also includes bonding the first and second components. The bonding can be performed by applying a UV adhesive and exposing the UV adhesive to UV radiation.
In another aspect, this invention includes a gripper for holding a component of an optical head. The gripper comprises a first jaw and a second jaw connected together at a pivot point, the first jaw comprising a first straight edge, and second jaw comprising second and third straight edges, the straight edges between positioned on the jaws such that the first straight edge is located between the second and third straight edges when the jaws are closed.